PRIORITY CLAIM
BACKGROUND
[0002] The use of radar to detect threats to the wingtips of aircraft faces the problem
that, for large aircraft with wide wingspans, many features commonly found around
airports, such as ground vehicles and personnel, lane markers, and runway drains,
may all serve to trigger false threats when the wing, and the sensor, approach or
pass over them. Anticollision systems must have very low false-alarm rates to be useful
to the operators. The use of very narrow beam patterns to distinguish threats fails
due to the general ratio of wing height versus range, which can be as much as 100:1,
see FIGURE 1. So the ability to actually determine the height of the object, or in
the case of hangar opening proscenia (the upper clearance) becomes very important.
SUMMARY
[0003] The present invention provides systems and methods for creating a narrow vertical
pathway of detection that permits the enforcement of a fixed "exclusion zone" that
is narrow and does not widen with range. An advantage to this approach is that the
zone or corridor does not widen with range, permitting a fixed exclusion zone that
will ignore items that will pass above or below the wing.
[0004] An exemplary system located on a vehicle includes at least two vertically separated
antennas that receive radar reflection signals, a processor, and an output device.
The processor receives the radar reflection signals received by the antennas, determines
vertical position of any obstacles identified by the radar reflection signals, and
determines if the obstacles are within a predefined alert zone. The output device
outputs an alert if any obstacle is within the alert zone. The predefined alert zone
is related to a protruding portion of the vehicle.
[0005] In one aspect of the invention, the processor further determines the vertical position
by taking a phase differential of corresponding radar reflection signals and determining
vertical position based on the phase differential.
[0006] In another aspect of the invention, the protruding portion of the vehicle includes
at least one of a portion of a wing or a portion of a nacelle attached to the wing.
[0007] In yet another aspect of the invention, the system includes a memory device that
stores obstacle information, based on associated determined vertical position information,
in a three-dimensional buffer.
[0008] In still another aspect of the invention, the predefined alert zone includes a volume
of space along at least one of a projection forward of a vehicle structure or a current
path of the vehicle structure.
[0009] In a further aspect of the invention, the predefined alert zone has a constant upper
limit, a constant lower limit, a first distance limit, and a second distance limit,
wherein the shape of the predefined alert zone is based on the vehicle structure that
the predefined alert zone relates to.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Preferred and alternative embodiments of the present invention are described in detail
below with reference to the following drawings:
[0011] FIGURE 1 is a side view of an aircraft that is implementing a wingtip collision-avoidance
system according to an embodiment of the present invention;
[0012] FIGURE 2 is a schematic image of a vehicle formed in accordance with an embodiment
of the present invention;
[0013] FIGURE 3 is a side view of an aircraft with a determined exclusion zone;
[0014] FIGURE 4 is a top view of the aircraft with the exclusion zone;
[0015] FIGURE 5 is graph showing representative beampatterns of a notional sensor having
a two channel input used for incoming signal phase detection;
[0016] FIGURE 6 is graph showing the relative phase offset from a given target height;
[0017] FIGURE 7 is a user interface image generated by the system shown in FIGURE 2; and
[0018] FIGURES 8 and 9 are side and top views of an aircraft with a determined wing and
nacelle exclusion zone.
DETAILED DESCRIPTION OF THE INVENTION
[0019] In one embodiment, as shown in FIGURE 2, an aircraft 20 includes an exemplary airport
surface collision-avoidance system (ASCAS) 18. The ASCAS 18 includes horizontally
and vertically discriminating radar sensors 26 included within aircraft light modules
30 or located at the other positions (e.g., vertical tail) about the aircraft 20.
The light modules 30 also include navigation/position lights 34, a processor 36, and
a communication device 38. The sensors 26 are in communication via the communication
device 38 (wired or wirelessly) to a user interface (UI) device 44.
[0020] In one embodiment, the UI device 44 includes a processor 50 (optional), a communication
device (wired or wireless) 52, and alerting device(s) 54. The UI device 44 provides
audio and/or visual cues (e.g., via headphones, tablet PC, etc.) based on sensor-derived
and processed information.
[0021] Based on information from the radar sensors 26, the UI device 44 provides some or
all of the following functions: detect and track intruder obstacles, evaluate and
prioritize threats, radar control, and declare and determine actions. Once an alert
associated with a detection has been produced, then execution of a collision-avoidance
action (e.g., stop the aircraft, maneuver around obstacle, etc.) is manually performed
by the operator or automatically by an automated system (e.g., autobrakes).
[0022] In one embodiment, processing of the radar information is done by the processor 36
and/or the processor 50 at the UI device 44.
[0023] In one embodiment, the antennas are installed at other fuselage areas, such as above
each engine or at the nose of the aircraft, etc. Even though the antennas are not
at the wingtip, the reflection data (radar return data) is buffered (stored), thus
allowing the image 120 to be displayed.
[0024] The information from multiple radar systems may be used to attain full coverage relative
to the aircraft 20, the wingtips, nacelles, and/or other aircraft structures. In one
embodiment, all radar reflection data is stored in a three-dimensional buffer referenced
to the vehicle (e.g., aircraft).
[0025] The pilot is alerted aurally, visually, and/or tactilely. For example, a visual alert
presented on an electronic flight bag (EFB) display shows aircraft wingtips outlined
or a highlight of any obstructions. Aural alerting is through existing installed equipment,
such as the interphone or other warning electronics or possibly the enhanced ground
proximity warning system (EGPWS) platform.
[0026] In one embodiment, two antennas (or two antenna arrays) arranged vertically and spaced
at a precise interval (e.g., λ/2 (half wavelength)). A single radar pulse is emitted
from the two antennas or a third antenna. Any radar pulse returns (reflections) are
received by the vertically separated antennas. The return signals are sent to the
processor (36, 50) that determines vertical position of an obstacle (i.e., performs
vertical discrimination) based on a determined phase differential between two corresponding
received return signals.
[0027] The processor (36, 50) determines horizontal and vertical information for obstacles
based on the horizontal and vertical discriminations performed on the raw radar return
signals. If any identified obstacles are located both horizontally and vertically
within a previously defined wingtip protection zone 66 that extends forward vertically
and laterally from a wingtip of an aircraft 62 - see FIGURES 3 and 4, the identified
obstacle is treated as a possible threat. An alert for all threats is outputted to
the operator of the aircraft 62.
[0028] The antennas can be implemented in many ways. In one embodiment, a 4 x 2 array of
antenna elements allows for a four input digital beamforming algorithm to discriminate
targets in the horizontal direction and a two input monopulse discrimination of targets
in the vertical direction. There are many different schemes for implementing the digital
beamforming and monopulse. Monopulse discrimination is implemented as a phase comparison
via a simple equation:
where λ is the wavelength of the radar frequency,
d is the distance between the antenna elements,
Δφ is the phase difference of the received signals of the two elements, in radians,
R is the range to the target determined by the radar, and
Δ
z is the vertical offset of the target from the antenna boresight.
[0029] The sign of the offset indicates whether the target is above or below the boresight.
[0030] In one embodiment, the processor (36, 50) stores obstacle information in a three-dimensional
buffer, where the wingtip protection zone 66 includes a subset of information (i.e.,
cells, voxels) from the three-dimensional buffer. The phase differential is used to
determine if any of the detected obstacles are in the "exclusion zone" through which
the wing will travel. Objects above or below this exclusion zone may be ignored. In
this example, a runway sign 68 and service truck 70 are shown in front of the aircraft
62. The runway sign 68 and service truck 70 are not considered a threat to the wing/wingtip
of the aircraft 62 because the are below the wingtip protection zone 66.
[0031] FIGURE 5 shows representative beampatterns of a notional sensor having a two channel
input used for incoming signal phase detection. The use of a wide field of view sensor
having the given wide pattern characteristics alone provides range capability only
to a given target. The use of the dual channels, and through the use of phase comparison
as described above, permits the simple sensor to perform angular location on the target
and permits the determiniation of height, or in the case of proscenium signs or thresholds,
the projection downward, and extent of the target.
[0032] FIGURE 6 shows how the dual channel (in each plane, but the elevation is shown here)
receiver can determine the vertical placement of the target via phase comparison,
and that the resulting phase differentials are easily measured to provide a height
to accuracies that permit the establishment of the required "safe zone" for passage
of the wing and/or the nacelles.
[0033] FIGURE 7 shows a top-down image 120 presented on a display that is part of the alerting
device 54. The image 120 includes an ownship aircraft icon 126 with two radar beam
coverage areas 124 that project forward from wingtips of the icon 126. The coverage
areas 124 show only what is identified as being within the zone 66. Two range rings
132, 134 arbitrarily placed at maximum and half range are shown on the image 120 at
fixed distances in front of the wing and can be scaled using either an interface on
the EFB or iPad or the cursor control device (CCD) in the aircraft, when shown on
a navigation display.
[0034] As shown in FIGURES 8 and 9, another aircraft 80 has expanded protection zones 84.
The expanded protection zone 84 includes a protection volume ahead of part of the
aircraft's wings and engine nacelles. The zone 84 is thicker vertically along the
projected path of the below wing engine nacelles. The zone 84 may be modified to provide
a protection zone around any structure that extends above or below the wing. In this
example, the runway sign 68 and the service truck 70 are considered a threat to the
wing/wingtip of the aircraft 62 because their corresponding radar reflection signals
appear within the expanded protection zone 84.
1. A system located on a vehicle, the system comprising:
at least two vertically separated antennas configured to receive radar reflection
signals;
a processor configured to:
receive the radar reflection signals received by the at least two vertically separated
antennas,
determine vertical position of any obstacles identified in the radar reflection signals,
and
determine if the obstacles are within a predefined alert zone; and
an output device configured to output an alert if any obstacle is within the predefined
alert zone, wherein the predefined alert zone is related to a protruding portion of
the vehicle and defined by whether the motion of the vehicle will result in collision
with an object located therein.
2. The system of claim 1, wherein the processor is further configured to determine the
vertical position by at least taking a phase differential of corresponding radar reflection
signals, and determining vertical position based on the phase differential.
3. The system of claim 1, wherein the protruding portion of the vehicle comprises at
least one of a portion of a wing or a portion of a nacelle attached to the wing.
4. The system of claim 1, further comprising a memory device configured to store obstacle
information in a three-dimensional buffer based on associated determined vertical
position information.
5. The system of claim 4, wherein the predefined alert zone comprises a volume of space
along at least one of a projection forward of a vehicle structure or a current path
of the vehicle structure.
6. The system of claim 5, wherein the predefined alert zone has a constant upper limit,
a constant lower limit, a first distance limit and a second distance limit, wherein
the shape of the predefined alert zone is based on the vehicle structure that the
predefined alert zone relates to.
7. A method comprising:
at at least two vertically separated antennas, receiving radar reflection signals;
at a processor:
receiving the radar reflection signals received by the at least two vertically separated
antennas,
determining vertical position of any obstacles identified in the radar reflection
signals, and
determining if the obstacles are within a predefined alert zone; and
at an output device, outputting an alert if any obstacle is within the predefined
alert zone, wherein the predefined alert zone is related to a protruding portion of
the vehicle and defined by whether the motion of the vehicle will result in collision
with an object located therein.
8. The method of claim 7, wherein determining the vertical position comprises:
taking a phase differential of corresponding radar reflection signals; and
determining vertical position based on the phase differential.
9. The method of claim 7, wherein the vehicle is an aircraft and the protruding portion
of the aircraft comprises at least one of a portion of a wing or a portion of a nacelle
attached to the wing.
10. The method of claim 7, further comprising storing obstacle information in a three-dimensional
buffer based on associated determined vertical position information.